Degumming process



Patented Mar. 1, 1927.

LYLE N. GILLIS, OF ROSECRES'I, VIRGINIA.

DEGUMMING PROCESS.

No Drawing.

This invention relates to the production of linen fiber and has special reference to a process for treating flax straw to separate the fibers from the remainder of the straw.

It is a well understood fact that all true linen is produced from the flax plant and that this has been done by various processes, such being known as retting and needing no description here further than to say that the common forms of retting employ bacteriological fermentation on the whole straw for the elimination of the gums and pectins, after which the straw is dried, scutched or beaten, and hackled.

In some processes it has been sought to use chemicals as solvents for these gums and resins but such processes as are now known are subject to serious objections. In some the cost of the chemicals which it is proposed to use is prohibitive. In others injury is; done the fiber and this is especially so when it is attempted to use an alkaline solvent on whole straw as the outer fibers are over exposed to the action of the alkali before the gums and pectins surrounding the inner fibers are dissolved.

Further in those employing alkaline sol vents no provision is made'to prevent softening of the fibers themselves by the action of the alkali though, in some cases, efforts have (1 been made to harden the fibers after actionof the alkaline solvent but such efforts have not met with success since, once the fibers have been softened it is not possible to restore their hardness without sacrificing elasticity and other important qualities which make for long life and strength in the material manufactured from these fibers.

Furthermore, in the processes heretofore employed, especially where retting of whole flax straw is carried out, it is impossible to obtain uniformity of product in the batch under treatment owing to the different straws being of different thickness and, in addition, no two batches are uniform in general qualities such as fineness of fiber, strength and the like.

Still further, with the usual processes of retting it is impossible to obtain good fiber from flax that has been allowed to go to seed andthe straw must be pulled before the seed has fully formed and ripened. Consequently, the flax has been heretofore raised, for textile purposes, and harvested in a special manner and the valuable seed product has been disregarded. This inability to use Application filed June 18, 1925. Serial No. 37,996.

straw derived from seed flax arises from the fact that the seed, in ripening, absorbs a large proportion of the oil in the straw and theremainder left in the fibers is so slight that the bacteria and chemicals heretofore used attack and destroy this remainder and leave the fibers too brittle to be spun.

In view of the above objections to the known processes of producing linen fiber from flax straw, the present invention has for its objects:

First: To provide an improved process of treating the straw wherein the chemicals used will be of extreme cheapness.

Second: To provideanovel process wherein all fibers will be equally exposed to the action of the chemicals.

Third: To provide an improved chemical process wherein an alkaline solvent will be used but having its effect so modified that the fibers obtained are not softened or weak ened but are kept in their original elastic conditions.

Fourth: To provide an improved process wherein uniform treatment of all fibers both in the batch and in successive batches may be assured thereby producing a uniform grade of product, which grade may be regulated in accordance with commercial reuirements.

Fifth: To provide an improved process wherein the straw from seed flax may be successfully used to produce suitable linen fibers for use in thread, twines and the like.

With the above and other objects in View, as will be hereinafter apparent, the invention consists in a. novel process for treating flax straw for the production of linen fibers wherein an improved order of steps and a new combination of chemicals will be used to produce the required results.

In carrying out this process the general steps employed are, first; crushing the straw and eliminating as far as possible the so called shives; next degumming in a special chemical bath; rinsing to remove the major part of the chemicals; washing in a soap solution; again rinsing; neutralizing any remaining chemicals, and giving the batch a final rinsing; and then drying.

Considering these steps one by one the process is developed in the manner now to be explained.

In order to crush the straw in the proper manner it mustbe dry, This drying may be accomplished in the course of curing in the room by the use of hot air care bein that the air is not too hot as thisren ers the fibers brittle and weak. It has been found by experience that it is Well, even wlth straw cured in the best manner in the field, to sub- .ject all straw to a preliminary drying at a temperature not to exceed 120 degrees Fah renheit, the time of exposure being regulated b the condition of the straw. It is obvious t at the air in the dryer-should be kept in circulation either by convection or mechanical means. ment in this manner is quite suflicient for the straw. The crushing or deshiving is effected on a suitable machine, such as that shown and described in my copending application filed of even date herewith and bearing the SerialNumber 37,995, wherein the straw will be bent back and forth without subjecting the fibers to a tensilestress sufiicient to strain them. Great care must be taken in this respect since breakage or undue stress on the fibers will roduce a weak linen fiber totally unsuitable For use in a commercial textile though such short or brokenfibers may well be used in paper making since they are, in such case interlaced and are not arranged side by side as in threads, twines and the like After the desliiving is accomplished there.

remains a mass of parallelstrips or ribbons each consisting of a multiplicity of fibers bound together by the gums and pectins of the straw. As turned out by my machine these strips are paper thin, being ap proximately about four thousandths of an inch thick and vary in width from about one sixt -fourth to one sixteenth of an inch. The strips are gathered from the machine and preferably laid in reticulated trays each havinga reticulated cover so that the strips are kept, during future treatments, in parallelism. However, as an alternative, the strips may be gathered into hanks tied loosely at the middle though this is not so effective. It is obvious that the material of which the trays and covers are made must be such as to be unaffected by the chemicals employed to any degree which will interfere with the process. To this end I have found copper to be a suitable metal for such trays.

These trays are then placed in a hot bath, preferably of a solution of sodium hydroxide, the sodium hydroxide being commercial sodium hydroxide of 90% strength, and bichromate of potash (commercial) in water. This bath is made by dissolving one and threequarter pounds of sodium hydroxide in twelve gallons of water and adding to the solution three and one-half ounces of. potassium bichromate. This solution is kept boiling slowly and the trays are immersed Usually, fifteen minutes treat-- therein for from 10 to 20 minutes depending on the character of the straw being treated and the fineness of the fiber to be produced.

After the treatment in this solution, which is the true degumming solution, the trays are removed and placed in a bath of warm water which is preferably running water or is kept agitated by suitable means. From here the trays are transferred to, a "third bath containing a neutral soap solution in which the fiber is Washed to, as far as possible, remove the chemicals and the dis-' solved gums which may remain after rinsing. From this bath the trays are transferred to a second rinsing bath which may be of cold waterand the fiber is rinsed to remove the soap. At this stage of the process the fiber is substantially clean with the exception that some slight traces of sodium hydroxide may remain and it is essential to the life of the linen that these traces be neutralized. Accordingly the trays are removed from the second rinsing bath and placed for about one-half minute in a bath containing a neutralizing solution of .sulphuric acid which is preferably free from discoloration, the solution being about onehalf of one per cent of acid in Water. Finally the fibers are again rinsed thoroughly to remove all traces of sulphuric acid and are dried.

After the drying process it will be found that the fibers are very readil hackled to straighten them out and that little loss results in the hackling process.

It will be observed that this process is such that the fibers may be made of any fineness desired in commercial production, the grade of fineness being controlled by the length of time the fibers are left in the degumming bath. Moreover the fibers produced in this manner are of the natural flax color the tint dependin on the color of the straw and due to the ardening agent, bichromate potash employed, the cells of the fabric retain the natural oil so that such fabrics have a very high de cc of strength and all of their natural e asticity. Tests have shown that fabrics prepared in this manner have a greater strength when twistthe straw and subjecting the straw to a neutralizing bath.

3. That process of degummin flax straw and the like which includes su jecting the straw to a bath containing sodium hydroxide and potassium bichromate in solution, washing the straw, and subjecting the straw to a neutralizing bath.

4. That process of degumming flax straw and the like which includes subjecting straw to an alkaline degumming bath contalning a hardening agent, washing the straw, and subjecting the straw to a neutralizing bath containing a solution of sulphuric aci 5. That process of degumming flax straw and the like which includes subjecting the straw to a degumming' bath containing a chromium derivative in solution, washing the straw, and subjecting the straw to a neutralizing bath containing a solution of sulphuric acid. I

6. That process of degumming flax straw and the like which includes subjecting the straw toa bath containing sodium hydroxide and potassium bichromate in solution, washing the straw, and subjecting the straw to a neutralizing bath containing a solution of sulphuric acid.

7 That process of degumming flax straw and the like which includes subjecting straw to an alkaline degumming bath containing a hardening agent, washing the straw, subjecting the straw to a neutralizing bath, and finally rinsing the straw in water until all traces of acid have been removed.

8. That process of degumining flax straw and the like which includes subjecting the straw to a degunnning bath containing a chromium derivative in solution, washing the straw, subjecting the straw to a neutralizing bath, and finally rinsing the straw in water until all traces of acid have been re.-

moved. I

9. That process of degumming flax straw and the like which includes subjecting the 11. That process of de g flax straw and the like which includes subjecting the straw to a degumming bath containing a chromium derivative in solution, washing the straw, subjecting the s raw to a neutralizing bath containing a solution of sulphuric acid, and finally rinsing the straw in water until alltraces of acid have been removed.

12. That process of degumming flax straw and the like which includes subjecting the straw to a bath containing sodium hydroxide and potassium bichromate in solution, wash ing the straw, subjecting the straw to a neutralizing bath containing a solution of sulphuricacid, and finally rinsing the straw in water until all traces of acid have been removed.

In testimony whereof I aifix' my signature.

LYLE N. GILLIS. 

